The problems presented by substances which deplete the atmospheric ozone layer were dealt with at Montreal, where the protocol was signed imposing a reduction in the production and use of chlorofluorocarbons (CFCs). This protocol has been the subject of amendments which have required the abandoning of CFCs and have extended the regulations to other products, including hydrochlorofluorocarbons (HCFCs).
The refrigeration and air-conditioning industry has invested a great deal in the replacement of these refrigerants and it is because of this that hydrofluorocarbons (HFCs) have been marketed.
In the motor vehicle industry, the air-conditioning systems of vehicles sold in many countries have been changed from a chlorofluorocarbon (CFC-12) refrigerant to a hydrofluorocarbon (1,1,1,2-tetrafluoroethane: HFC-134a) refrigerant, which is less harmful to the ozone layer. However, from the viewpoint of the objectives set by the Kyoto protocol, HFC-134a (GWP=1430) is considered to have a high heating power. The contribution of a refrigerant to the greenhouse effect is quantified by a criterion, the GWP (Global Warming Potential), which summarizes the heating power by taking a reference value of 1 for carbon dioxide.
Hydrofluoroolefins (HFOs) have a low heating power and thus meet the objectives set by the Kyoto protocol. Document JP 4-110388 discloses hydrofluoropropenes as heat-transfer agents.
In the industrial sector, the refrigerating machines most commonly used are based on cooling by evaporation of a liquid refrigerant. After vaporization, the refrigerant is compressed and then cooled in order to return to the liquid state and thus continue the cycle.
The refrigeration compressors used are of the reciprocating, scroll, centrifugal or screw type. In general, internal lubrication of the compressors is essential in order to reduce wear and heating of the moving members, complete their leaktightness and protect them against corrosion.
In addition to good heat-transfer agent properties, in order for a refrigerant to be commercially accepted, it must in particular exhibit thermal stability and compatibility with the lubricants. Specifically, it is highly desirable for the refrigerant to be compatible with the lubricant used in the compressor, present in the majority of refrigeration systems. This combination of refrigerant and lubricant is important for the implementation and the efficiency of the refrigeration system; in particular, the lubricant should be sufficiently soluble or miscible in the refrigerant over the entire operating temperature range.
Thus, polyalkylene glycols (PAGs) have been developed as lubricants of HFC-134a in motor vehicle air conditioning.
Tests for miscibility of 1,1,3,3,3-pentafluoropropene and 1,3,3,3-tetrafluoropropene with lubricants have been described in Example 2 of document WO 2004/037913. Compatibility tests have also been described in Example 3, with polyalkylene glycol. However, these tests do not specify the nature of the 1,3,3,3-tetrafluoropropene isomer.
Moreover, document WO 2005/108522 discloses an azeotropic composition of trans-1,3,3,3-tetrafluoropropene and 1,1,1,2-tetrafluoroethane.
Just recently, 2,3,3,3-tetrafluoropropene was chosen as a refrigerant for replacing HFC-134a in motor vehicle air conditioning.